The Flow Cytometry Unit provides extensive support for NCI clinical protocols by providing diagnostic testing for leukemia and lymphoma in patient either on NCI clinical protocols or undergoing testing to determine eligibility for said protocols. The Flow Cytometry Unit provides clinical flow cytometric evaluation of blood, bone marrow, fine needle aspirates, tissue biopsies and body fluids for hematolymphoid neoplasia in NCI patients. The majority of flow cytometric testing performed by the Flow Cytometry Unit involves detection of minimal residual disease (patients are status post therapy at outside institution prior to enrollment on NCI protocol) and measurement of specific tumor cell characteristics mandated by various clinical protocols. Significant effort in the unit is devoted to delivery of numerous unique protocol mandated assays that are not offered by commercial laboratories. The Flow Cytometry Unit is also actively engaged in education of the NIH staff and medical community at large in the proper utility of flow cytometry in medical practice. The utility of flow cytometric analysis in leukemia and lymphoma gained acceptance in the late 1980s. Since that time there has been growing concern among practitioners in the field of clinical flow cytometry about inconsistent practices as well as deficiencies in standardization and validation and its possible impact on patient care. To address this issue a group of U.S. and Canadian hematopathologists, hematologists and laboratory scientists met in Bethesda, MD from November 16-17, 1995 to develop the U.S.-Canadian Consensus Recommendations on the Immunophenotypic Analysis of Hematologic Neoplasia by Flow Cytometry. The consensus document produced provided guidance on standardization and validation of laboratory procedures, data analysis and interpretation and data reporting. Guidelines were also provided on medical indications for testing. Although consensus could not be reached at that time on the number or combination of antibodies utilized in flow cytometric evaluation of leukemia or lymphoma, strategies were provided for the selection of antibodies and lists of markers useful in identification of acute leukemias and lymphoproliferative processes were provided. Recently there was growing recognition of the need to set standards of training and education for practitioners in the field of flow cytometry, including technologists, interpreters and laboratory directors. It was also realized that the previous guidelines on medical indications for flow cytometric testing were no longer practical and that new guidelines on medical indications for flow cytometric analysis that are based upon clinical signs and symptoms suggestive of hematolymphoid neoplasia are needed in the field. Similarly, guidelines on antibody panels recommended for patients presenting with specific signs and symptoms are desirable. To address these issues the Flow Cytometry Unit, CCR, NCI, NIH organized the 2006 Bethesda International Consensus Conference on Flow Cytometric Immunophenotyping of Hematolymphoid Neoplasia. During this conference the important issues and goals were identified and a structure defined to achieve the identified goals. The final consensus recommendations on training, medical indications and antibody panels generated by this process were published in September 2007. A new consensus process in underway to determine optimal diagnostic antibody panels for various disease processes. The flow cytometry Unit participated in an international consensus group determining optimal methodology for diagnostic evaluation of cerebral spinal fluid for hematolymphoid neoplasia. The results on this consensus process have recently been published. The Flow Cytometry Unit, CCR, NCI, NIH has been instrumental in producing the regulatory document on flow cytometric immunophenotyping of lymphoma and leukemia, Clinical and Laboratory Standards Institute. Clinical Flow Cytometric Analysis of Neoplastic Hematolymphoid Cells; Approved Guideline-Second Edition. CLSI document H43-A2 . This guideline will be used as the gold standard when laboratories performing flow cytometric analysis of hematolymphoid malignancies in the United States are inspected by CLIA/CAP. It provides detailed technical guidelines for laboratory procedures involved in flow cytometric testing of hematolymphoid neoplasia. The Flow Cytometry Unit has studied the immunophenotypic characteristics of familial and sporadic chronic lymphocytic leukemia. Familial chronic lymphocytic leukemia (CLL) families are being studied because they potentially provide a unique opportunity to study the development of CLL, a common neoplasm. We have studied the immunophenotypic profiles of patients with sporadic CLL and with familial CLL and found significant differences between the two groups. Furthermore, the association of prognosis with the cell surface protein profile differs between familial and sporadic CLL.